The quantity of data used in a computer system has increased rapidly in recent years. As a storage system for managing such data, a large-scale storage system managed by a RAID (Redundant Arrays of Inexpensive Disks) method for providing huge storage resources as called mid-range class or enterprise class has attracted public attention recently.
A storage system called NAS (Network Attached Storage) has been also developed so that the storage system and each information processor are connected to each other by a network using a protocol such as TCP/IP (Transmission Control Protocol/Internet Protocol) etc., to achieve access at file level from the information processor (e.g., JP-A-8-212095).
On the other hand, a technique called fail-over has been developed so that, even if failure occurs in an information processor using a storage region provided by a storage system, another information processor can be used in place of the failed information processor for performing processing to continue provision of service by the information processor.